1. Field of Invention
This invention relates to apparatus for adjusting the tension and height of volleyball nets.
2. Prior Art
Volleyball regulations require a specific net height and tension. Net height is different for men and women, and since both sexes use the same courts at different times, it is often necessary to readjust nets. Also, volleyball nets and standards at most facilities are regularly taken down for other court uses, such as basketball. Thus it would be very useful to have equipment that can be quickly and easily set-up, adjusted, and removed.
Most existing equipment lacks this convenience. The readjustment procedure on basic poles has been to disconnect the net cables and net-edge cords from the poles, move them to new attachment points, and re-tighten them. This is time consuming and difficult. The upper attachment point is about 2.43 meters (8 feet) above the ground, making it hard to reach. The required cable tension is hundreds of kilograms (over 500 lbs.) in the upper cable, preferably both, for net sag no greater than 2 cm. (3/8 in.) as required in current U.S. Volleyball Association regulations.
A winch is sometimes provided to make proper net tensioning feasible, but often only the upper net cable is winched. A relatively slack lower cable results in poor rebound of a ball striking the net. Sometimes a winch is provided for both the upper and lower net cables. This complicates winch positioning, forcing at least one winch to a non-optimum location on the pole (above easy reach, for example, or below the lower cable, which is a player-collision hazard). It also adds the weight and expense of the second winch.
One source of adjustment delay is iteration, or alternate tightening of the upper and lower cables until the right combination of tension and net height is approximated. When the upper cable is tightened the net rises, and when the lower cable is tightened, the net is pulled lower. Often several iterations are required, with optimum cable tension finally compromised in favor of reasonably accurate height at net center.
One type of system provides a winch on each pole--one for each cable. Adjustment requires the user to walk back and forth between the two poles during iteration, which is very inconvenient.
Another system uses a telescoping standard, to make vertical repositioning of the hardware easier. However, the upper section slides into the lower section, making it impractical to mount all the net-connection hardware on the movable section.
Another system uses a separate slide bar for each end of each cable, plus another slide bar for the winch. This requires three separate slide adjustments on the winch end of the standard, and two on the opposite end, for a total of 5. Only the upper cable is winched. A separate pulley tensioner is offered for the lower cable. As with the others, tension adjustment is iterative.
Current systems ignore the importance of proportional tension in the lower net cable to achieve ball rebound. Rebound is possibly the second major net criterion to tournament players, after accurate height. Some systems are complex and expensive, but provide only minor benefits. None of the systems with infinite vertical adjustment can use existing poles. None appear suitable for beach doubles courts, which require a wide range of adjustment.
The related invention, referenced earlier, solves these disadvantages by routing a single winch cable to both the upper and lower net cables via pulleys, and offering a vertically-slidable mount on each pole, to which the winch and all net-connection hardware can be attached.
The present invention solves the same disadvantages in a different way, as fully described herein.